Question

So I have two classes.
One is a class called Main. The Main class is supposed to process some data.

Then I have another class called MainApplet, an Applet of course.
How can I display MainApplet from the Main class? This is what I have so far, but the applet does not show:

public class Main {
public static void main(String args[]) {
    System.out.println("Starting application.");

    MainApplet Main = new MainApplet();
    Main.setVisible(true);
    Main.show();
} }

Answer 1

How can I display MainApplet from the Main class?

You don’t. You display an applet from HTML code.

Are you sure your GUI is in fact an applet? Does it extend JApplet or Applet? If so and you want to show it on the desktop through code, then don’t make it an applet but instead display a JFrame. The Java Swing tutorials will show you how to do this: How to use Swing Components

Edit
you state:

Basically I have a Main class that is not an applet. It doesn’t extend anything. Then I have another class named MainApplet that is an applet (extends JApplet). I want to run Main first, then display MainApplet after… but I can do it the other way around if needed.

You don’t sound like you’re running your code from a web page (for some reason you’re still keeping this information from us), so the solution is not to use applets for this. Instead create a JFrame. Please check out the tutorials that I’ve linked to above since an applet is not appropriate for your needs.

You will have a main that creates your GUI, that passes any information into the GUI via constructor or method parameters, and then that tells the GUI to show itself (by calling setVisible(true) if it’s a JFrame).